package mpegps

import (
	"bytes"
	"errors"
)

const (
	CodecUnknown = iota
	CodecH264
	CodecH265
	CodecH266
	CodecMpeg4
)

var crc32table [256]uint32 = [256]uint32{
	0x00000000, 0xB71DC104, 0x6E3B8209, 0xD926430D, 0xDC760413, 0x6B6BC517,
	0xB24D861A, 0x0550471E, 0xB8ED0826, 0x0FF0C922, 0xD6D68A2F, 0x61CB4B2B,
	0x649B0C35, 0xD386CD31, 0x0AA08E3C, 0xBDBD4F38, 0x70DB114C, 0xC7C6D048,
	0x1EE09345, 0xA9FD5241, 0xACAD155F, 0x1BB0D45B, 0xC2969756, 0x758B5652,
	0xC836196A, 0x7F2BD86E, 0xA60D9B63, 0x11105A67, 0x14401D79, 0xA35DDC7D,
	0x7A7B9F70, 0xCD665E74, 0xE0B62398, 0x57ABE29C, 0x8E8DA191, 0x39906095,
	0x3CC0278B, 0x8BDDE68F, 0x52FBA582, 0xE5E66486, 0x585B2BBE, 0xEF46EABA,
	0x3660A9B7, 0x817D68B3, 0x842D2FAD, 0x3330EEA9, 0xEA16ADA4, 0x5D0B6CA0,
	0x906D32D4, 0x2770F3D0, 0xFE56B0DD, 0x494B71D9, 0x4C1B36C7, 0xFB06F7C3,
	0x2220B4CE, 0x953D75CA, 0x28803AF2, 0x9F9DFBF6, 0x46BBB8FB, 0xF1A679FF,
	0xF4F63EE1, 0x43EBFFE5, 0x9ACDBCE8, 0x2DD07DEC, 0x77708634, 0xC06D4730,
	0x194B043D, 0xAE56C539, 0xAB068227, 0x1C1B4323, 0xC53D002E, 0x7220C12A,
	0xCF9D8E12, 0x78804F16, 0xA1A60C1B, 0x16BBCD1F, 0x13EB8A01, 0xA4F64B05,
	0x7DD00808, 0xCACDC90C, 0x07AB9778, 0xB0B6567C, 0x69901571, 0xDE8DD475,
	0xDBDD936B, 0x6CC0526F, 0xB5E61162, 0x02FBD066, 0xBF469F5E, 0x085B5E5A,
	0xD17D1D57, 0x6660DC53, 0x63309B4D, 0xD42D5A49, 0x0D0B1944, 0xBA16D840,
	0x97C6A5AC, 0x20DB64A8, 0xF9FD27A5, 0x4EE0E6A1, 0x4BB0A1BF, 0xFCAD60BB,
	0x258B23B6, 0x9296E2B2, 0x2F2BAD8A, 0x98366C8E, 0x41102F83, 0xF60DEE87,
	0xF35DA999, 0x4440689D, 0x9D662B90, 0x2A7BEA94, 0xE71DB4E0, 0x500075E4,
	0x892636E9, 0x3E3BF7ED, 0x3B6BB0F3, 0x8C7671F7, 0x555032FA, 0xE24DF3FE,
	0x5FF0BCC6, 0xE8ED7DC2, 0x31CB3ECF, 0x86D6FFCB, 0x8386B8D5, 0x349B79D1,
	0xEDBD3ADC, 0x5AA0FBD8, 0xEEE00C69, 0x59FDCD6D, 0x80DB8E60, 0x37C64F64,
	0x3296087A, 0x858BC97E, 0x5CAD8A73, 0xEBB04B77, 0x560D044F, 0xE110C54B,
	0x38368646, 0x8F2B4742, 0x8A7B005C, 0x3D66C158, 0xE4408255, 0x535D4351,
	0x9E3B1D25, 0x2926DC21, 0xF0009F2C, 0x471D5E28, 0x424D1936, 0xF550D832,
	0x2C769B3F, 0x9B6B5A3B, 0x26D61503, 0x91CBD407, 0x48ED970A, 0xFFF0560E,
	0xFAA01110, 0x4DBDD014, 0x949B9319, 0x2386521D, 0x0E562FF1, 0xB94BEEF5,
	0x606DADF8, 0xD7706CFC, 0xD2202BE2, 0x653DEAE6, 0xBC1BA9EB, 0x0B0668EF,
	0xB6BB27D7, 0x01A6E6D3, 0xD880A5DE, 0x6F9D64DA, 0x6ACD23C4, 0xDDD0E2C0,
	0x04F6A1CD, 0xB3EB60C9, 0x7E8D3EBD, 0xC990FFB9, 0x10B6BCB4, 0xA7AB7DB0,
	0xA2FB3AAE, 0x15E6FBAA, 0xCCC0B8A7, 0x7BDD79A3, 0xC660369B, 0x717DF79F,
	0xA85BB492, 0x1F467596, 0x1A163288, 0xAD0BF38C, 0x742DB081, 0xC3307185,
	0x99908A5D, 0x2E8D4B59, 0xF7AB0854, 0x40B6C950, 0x45E68E4E, 0xF2FB4F4A,
	0x2BDD0C47, 0x9CC0CD43, 0x217D827B, 0x9660437F, 0x4F460072, 0xF85BC176,
	0xFD0B8668, 0x4A16476C, 0x93300461, 0x242DC565, 0xE94B9B11, 0x5E565A15,
	0x87701918, 0x306DD81C, 0x353D9F02, 0x82205E06, 0x5B061D0B, 0xEC1BDC0F,
	0x51A69337, 0xE6BB5233, 0x3F9D113E, 0x8880D03A, 0x8DD09724, 0x3ACD5620,
	0xE3EB152D, 0x54F6D429, 0x7926A9C5, 0xCE3B68C1, 0x171D2BCC, 0xA000EAC8,
	0xA550ADD6, 0x124D6CD2, 0xCB6B2FDF, 0x7C76EEDB, 0xC1CBA1E3, 0x76D660E7,
	0xAFF023EA, 0x18EDE2EE, 0x1DBDA5F0, 0xAAA064F4, 0x738627F9, 0xC49BE6FD,
	0x09FDB889, 0xBEE0798D, 0x67C63A80, 0xD0DBFB84, 0xD58BBC9A, 0x62967D9E,
	0xBBB03E93, 0x0CADFF97, 0xB110B0AF, 0x060D71AB, 0xDF2B32A6, 0x6836F3A2,
	0x6D66B4BC, 0xDA7B75B8, 0x035D36B5, 0xB440F7B1,
}

func CalcCrc32(crc uint32, buffer []byte) uint32 {
	var i int = 0
	for i = 0; i < len(buffer); i++ {
		crc = crc32table[(crc^uint32(buffer[i]))&0xff] ^ (crc >> 8)
	}
	return crc
}

type StartCodeType int

const (
	StartCode3 StartCodeType = 3
	STartCode4 StartCodeType = 4
)

func FindStartCode(nalu []byte, offset int) (int, StartCodeType) {
	idx := bytes.Index(nalu[offset:], []byte{0x00, 0x00, 0x01})
	switch {
	case idx > 0:
		if nalu[offset+idx-1] == 0x00 {
			return offset + idx - 1, STartCode4
		}
		fallthrough
	case idx == 0:
		return offset + idx, StartCode3
	}
	return -1, StartCode3
}

func SplitFrame(frames []byte, onFrame func(nalu []byte) bool) {
	beg, sc := FindStartCode(frames, 0)
	for beg >= 0 {
		end, sc2 := FindStartCode(frames, beg+int(sc))
		if end == -1 {
			if onFrame != nil {
				onFrame(frames[beg+int(sc):])
			}
			break
		}
		if onFrame != nil && onFrame(frames[beg+int(sc):end]) == false {
			break
		}
		beg = end
		sc = sc2
	}
}
func H264NaluType(h264 []byte) uint8 {
	loc, sc := FindStartCode(h264, 0)
	return h264[loc+int(sc)] & 0x1F
}
func H265NaluType(h265 []byte) uint8 {
	loc, sc := FindStartCode(h265, 0)
	return (h265[loc+int(sc)] >> 1) & 0x3F
}

func mpegH264FindNALU(data []byte) (int, int, error) {
	var zeros, i int

	for i = 0; i+2 < len(data); i++ {
		if data[i] == 0x01 && zeros >= 2 {
			return i + 1, zeros + 1, nil // 返回 NALU 的长度和前导零的数量
		}

		if data[i] == 0 {
			zeros++
		} else {
			zeros = 0
		}
	}

	return -1, 0, errors.New("no valid NALU found")
}

// 来自media-server
func mpegH26xVerify(data []byte) (int, error) {
	h264Flags := uint32(0x01A0)      // SPS/PPS/IDR
	h265Flags := uint64(0x700000000) // VPS/SPS/PPS
	h266Flags := uint32(0xC000)      // VPS/SPS/PPS
	count := 0
	h26x := [5][10]int{}

	p := 0
	end := len(data)

	for p < end && count < len(h26x[0]) {
		n, _, err := mpegH264FindNALU(data[p:])
		if err != nil {
			break
		}
		if p+n+1 > end {
			break
		}

		h26x[0][count] = int(data[p+n]) & 0x1F          // H.264 NALU type
		h26x[1][count] = (int(data[p+n]) >> 1) & 0x3F   // H.265 NALU type
		h26x[2][count] = (int(data[p+n+1]) >> 3) & 0x1F // H.266 NALU type
		h26x[3][count] = int(data[p+n])                 // MPEG-4 VOP start code
		h26x[4][count] = int(data[p+n+1])               // MPEG-4 VOP coding type
		count++

		p += n // 移动到下一个 NALU
	}

	for n := 0; n < count; n++ {
		h264Flags &= ^(1 << h26x[0][n])
		h265Flags &= ^(1 << h26x[1][n])
		h266Flags &= ^(1 << h26x[2][n])
	}

	if h264Flags == 0 && h265Flags != 0 && h266Flags != 0 {
		// match SPS/PPS/IDR
		return CodecH264, nil
	} else if h265Flags == 0 && h264Flags != 0 && h266Flags != 0 {
		// match VPS/SPS/PPS
		return CodecH265, nil
	} else if h266Flags == 0 && h264Flags != 0 && h265Flags != 0 {
		// match SPS/PPS
		return CodecH266, nil
	} else if h26x[3][0] == 0xB0 && (h26x[4][0]&0x30) == 0 {
		// match VOP start code
		return CodecMpeg4, nil
	}

	return CodecUnknown, nil
}
func audioVerify(data []byte) PsStreamType {
	if data[0] == 0xFF && (data[1]&0xF0) == 0xF0 && len(data) > 7 {
		aacLen := ((int(data[3]) & 0x03) << 11) |
			(int(data[4]) << 3) |
			(int(data[5]) >> 5 & 0x07)
		if len(data) == aacLen {
			return PsStreamAac
		}
	}
	return PsStreamG711A
}
